Researchers have developed an implantable sensor that measures blood sugar continuously and transmits the information without wires -- a milestone, they said, in diabetes treatment.

It takes the diabetes field a step closer to development of an "artificial pancreas" -- a device that can replace natural functions to control how the body handles blood sugar.

It is hoped that initial human testing can be initiated this summer.

The pig implant is about 1.5 inches in diameter and 5/8 inch thick, but plans to further reduce the size are being considered.

The Juvenile Diabetes Research Foundation, which helped pay for the study, has been working with several companies to create a seamless artificial pancreas. It works with U.S. drugmaker Johnson & Johnson's unit Animas, which makes insulin pumps, and DexCom Inc, which makes continuous glucose monitoring devices.

Smiths Medical, a unit of Smiths Group Plc, Abbott Diabetes Care, a unit of Abbott Laboratories Inc, and Medtronic Inc also make glucose and insulin devices.